Name That Engine Failure... Feel like I lost a child!

[DSM]

Couple videos for your enjoyment. Kevin right again. Didn't notice until watching videos. There are holes in both the piston and cylinder. Got awfully hot in there. My poor baby....

SON OF BEECH SHEET

View Thru Bottom Plug -----> https://drive.google.com/file/d/1mp0DlAEUaiLsD8G5zEiYZ43qzS1bmIHT/view?usp=drive_link

View Thru Top Plug -----> https://drive.google.com/file/d/1vVPy14E3Ut2zd-eScGDAc5pATROCFTV5/view?usp=drive_link

[flightlead404]

A little JB Weld and you'll be as good as new

[pmax]

Originally Posted by DSM

Run Video Link ---> https://drive.google.com/file/d/1gLuRuw6cBoxZeVBd2TZEOArKTqhOOVm-/view?usp=sharing
...

Did you feel up a hot engine with your bare hands ?

Way to get close to your car !

[MoreGAS]

Well it kind of appears you may have 98 MM 3.4 P/C combo as they may be 98s w that small dome(stock 97 mm do not have that nor a valve pocket) ? Did you get any other doc's when you bought the engine? I mention this as finding singles of those 98s , assuming only need 1 P/C pair may be harder to find...
Also, my experience w this situation is more akin to a cutting torch blowing a hole sideways through the cylinder , and it looks just like that, not a crack. Also often the ring lands of a piston or two will fall out in pieces when you pull the cylinder off....
The cylinder appeared to crack like a walnut. We lean more toward keeping the cylinders as strong as possible for a Tbo to improved power (leave 97mm, this is what we built last ) and stroke it for larger displacement 76.4 to maybe even 78.4 mm , or bore the case larger 2mm and make custom liners to 99 or 100 mm in stronger material pressed in ALum liners(on the drawing board) You can always increase the Boost 1 PSI to make up for the slightly smaller than 100 MM Bore size.

You'll have some deeper discovery to do ahead and not looking like a cutting torch hit it is good news !

Be well
Kevin
GAS Motorsport

[mikedsilva]

Such a clean combustion chamber.

[DSM]

Originally Posted by MoreGAS

Well it kind of appears you may have 98 MM 3.4 P/C combo as they may be 98s w that small dome(stock 97 mm do not have that nor a valve pocket) ? Did you get any other doc's when you bought the engine? I mention this as finding singles of those 98s , assuming only need 1 P/C pair may be harder to find...
Also, my experience w this situation is more akin to a cutting torch blowing a hole sideways through the cylinder , and it looks just like that, not a crack. Also often the ring lands of a piston or two will fall out in pieces when you pull the cylinder off....
The cylinder appeared to crack like a walnut. We lean more toward keeping the cylinders as strong as possible for a Tbo to improved power (leave 97mm, this is what we built last ) and stroke it for larger displacement 76.4 to maybe even 78.4 mm , or bore the case larger 2mm and make custom liners to 99 or 100 mm in stronger material pressed in ALum liners(on the drawing board) You can always increase the Boost 1 PSI to make up for the slightly smaller than 100 MM Bore size.

You'll have some deeper discovery to do ahead and not looking like a cutting torch hit it is good news !

Be well
Kevin
GAS Motorsport

Yes, was sold to me as 3.4. Original owner stated slightly higher compression than stock 930 so to have a bit more more off boost.

[DSM]

Originally Posted by flightlead404

A little JB Weld and you'll be as good as new

That would be great!

[DSM]

Originally Posted by pmax

Did you feel up a hot engine with your bare hands ?

Way to get close to your car !

Nice! Thanks

[Neil Harvey]

You still have work to do to find and fix the cause.

For future reference, your very first post showing the Spark plug told you you did not melt the Piston. The Spark plug looks clean.

It also is telling you your actual "in cylinder" Ignition lead.

[GJF]

Looks like there was some detenation on the intake side. It wasnt lean, but more than likely a little heavy on the timing at that boost setting. Detonation at high boost, will crack the cast cylinder. Not enough fuel will create heat and cause detonation, which would have torch a hole in the piston and crack or melt the cylinder too. Take the detonation and call it a win you really didnt want. Check the piston at it's ring lands for any signs of damage. I'm willing to bet there will be none. Find a replacement cylinder and put it back together. Set a overboost level and drive!

[DSM]

Okay have it torn down. Before removing cam gear I wanted to verify cam timing.

Set #1 TDC with Z1 located on case mark
#1 rocker is now loose and set to 0.004”
Rotate crank 1 revolution back to Z1
Dial indicator measuring 0.120” (3.048mm)
Now #4 rocker is loose and set to 0.004”
Move dial indicator to #4
Rotate crank 1 revolution to Z1 again.
Dial indicator measuring 0.119” (3.0226mm)
-
Are these numbers right? Do they seem high?
Stock turbo is 0.7mm and I see people stating they set theirs with sc cams between 1.4 to 1.7?
-
For reference, this is what I believe the engine build spec to be. This info was gathered from what I could actually see/verify and what was provided to me at time of purchase(Receipts/Documents provided by seller).

Case:
930/66
Cross drill @ #4 main journal, nitride and finish grind as necc.
Machine main webs: Boat Tail & increase oil passage dia. to #4.
Main Brg: Install 3mm piston squirters & shuffle pin case halves.
ARP Case studs, Nuts, & Washer Set

Crank: Factory 930 (Machined to GT-1 spec)

Cylinders: 98mm MAHLE Cylinders

Pistons: JE 98mm, 3.4L Turbo – Compression Ratio ?

Rods:
Pauter Machine
P/n: 964-230-580-1270F
Material: E4340 C’Molly Steel
Set ID#: J-1,30,32,62,85,106
Center to Center Length: 5.000
Overall weight: 596 grams

Camshaft:
Elgin 108 Lobe 296/276
Static Flow 10.8g/s @ 600KPa

Heads:
930 Twin Plug
Intake ports bored to 42mm
Port & polish intake and exhaust ports
Competition 3 angle valve job.

Valves:
Intake: ?
Exhaust: 930 105 419 50

Intake:
Factory Carrera 3.2

Intercooler:
Dp / Kremer

Engine Management:
Electromotive Tec3r (Upgraded Wintec 4)
Clewett Engineering Crank Pulley and Sensor
Clewett Engineering Scavenge Pump W/Cam Sync Sensor
Tps Sensor?
2 Bar GM Map Sensor
Bosch 2 Wire IAC
Mat Sensor?
CLT Sensor?

Injectors:
Siemens FI114961 63 lb/hr
Turn Off Time=.85ms @ 600KPa
Turn On Time=1.14ms @ 14VDc
Offset=.055ms
Gain=.110ms/mg
Impedance 12 Ohms (High)

Wideband: AEM FailSafe

Turbo Charger: Garrett GT35R, Dual Ball Bearings (Turbo Craft)

BOV: HKS Super Sequential (Part# 1421-SA001)

Fuel Pump: Bosch 044

Dyno Sheet (.9 Bar Boost)












Crack runs entire length of cylinder right along head stud. The two pics are at slightly different angles of #6 to show entire crack.
----------

[DSM]

Originally Posted by GJF

Looks like there was some detenation on the intake side. It wasnt lean, but more than likely a little heavy on the timing at that boost setting. Detonation at high boost, will crack the cast cylinder. Not enough fuel will create heat and cause detonation, which would have torch a hole in the piston and crack or melt the cylinder too. Take the detonation and call it a win you really didnt want. Check the piston at it's ring lands for any signs of damage. I'm willing to bet there will be none. Find a replacement cylinder and put it back together. Set a overboost level and drive!

Great advice and that's my plan.

What are you running for a knock sensor?

Thank you!

[DSM]

Originally Posted by krasuskyp

Ugh. The worst feeling. Bummer - btdt. Cracked cylinder may just be best case there tho - waaaay better than spun rods / mains (like mine ftmfl).

Best of luck with the fix from a fellow CT'er (I'm in Tolland)...

Agreed, way better scenario than dealing with rotating assembly.

Thanks!

[stownsen914]

Re: the cam, it looks like longer duration and has a narrower lobe center, so almost 3 mm of lift at overlap is believable.

[boosted79]

That engine deserves a set of Nickies.

[flightlead404]

sc cams 1.8mm. that's what mine are set to anyway

[GJF]

J&S Electronics SafeGuard Indivdual Cylinder Knock Control

Standalone knock system. These are the guys who practically invented it. Lots of variations but these guys are always there when you need them for any customer support. It is good extra insurance.

[onboost]

Those don't look like 98mm cylinders.. they should be full fin unless the stock ones were bored and plated.

[TurboKraft]

Originally Posted by onboost

Those don't look like 98mm cylinders.. they should be full fin unless the stock ones were bored and plated.

+1
Those are standard 1978-89 97mm "bald" cylinders i.e. no fins across the tops of the cylinders.

We've seen them fail this same way, along the clearance groove for the head stud, the thinnest point of the cylinder.

If they've been bored and re-plated, that's not good. It's taking an already weak design and making it weaker.

[DSM]

Originally Posted by GJF

J&S Electronics SafeGuard Indivdual Cylinder Knock Control

Standalone knock system. These are the guys who practically invented it. Lots of variations but these guys are always there when you need them for any customer support. It is good extra insurance.

GJF
This is my knock sensor. Where is yours located? Just curious. I’ve seen a few different setup. Installed this one because at the time engine was in car. This was the easiest to install. Again, I would use a custom table to run/tune it. Didn’t get that far but that was the plan.

Others
I know others have this setup. What are your experiences with how well it works or doesn’t.

Thanks!